I've never been too sure as to how CCL's "Past Guest" program works. We sailed on the Fantasy in '97 and again in '98, and never a PG recognition. It wasn't until we sailed on the Paradise in '99 that we got a letter from CCL with our PG number, and notification that we would receive a "complimentary two-year subscription to Currents Magazine". We've been receiving Currents ever since.
Maybe you have to take more than a 3- or 4-night cruise before they consider you to be PG material, but I'm not at all sure about that. There's a special PG service phone number (1-888-225-4837). Why don't you call and ask about your PG number? Good luck.
I don't have mine buy my husbands is on the current magazine we get. I did email carnival and asked them but they emailed me back that I had to call them to get it.
You can call Carnival and they can look it up.